After Domain Mapping 3.1.2 site, domain shows generic IIS home page and not blog content

OK, have a sub-directory multi-site blog operational for a while now. Bought the new domain and ready to go live. So I installed Domain Mapping on my IIS box (7.5.7600.16385) with the URL rewrite module installed. I did a Network Activate of the Domain Mapping plugin, made the changes the plugin suggested (uncommenting the “define( ‘SUNRISE’, ‘on’ );” in my wp-config.php file) and adding the IP address of the server in the Network Admin settings page. And when I click on the Site Admin page for the subdirectory blog I am attempting to map and go to Tools, Domain Mapping, I see an entry that I created for:

Custom Domain

Original Domain

But when I try to browse to I only see the generic IIS landing page, not any of the blog content. When I ping by name, it resolves to the correct IP address of the server, which appears in the Network Admin settings page mentioned above.

What am I missing to get this working correctly?